Question: Solve for $x$ and $y$ using substitution. ${3x-2y = -4}$ ${x = -y-3}$
Answer: Since $x$ has already been solved for, substitute $-y-3$ for $x$ in the first equation. ${3}{(-y-3)}{- 2y = -4}$ Simplify and solve for $y$ $-3y-9 - 2y = -4$ $-5y-9 = -4$ $-5y-9{+9} = -4{+9}$ $-5y = 5$ $\dfrac{-5y}{{-5}} = \dfrac{5}{{-5}}$ ${y = -1}$ Now that you know ${y = -1}$ , plug it back into $\thinspace {x = -y-3}\thinspace$ to find $x$ ${x = -}{(-1)}{ - 3}$ $x = 1 - 3$ ${x = -2}$ You can also plug ${y = -1}$ into $\thinspace {3x-2y = -4}\thinspace$ and get the same answer for $x$ : ${3x - 2}{(-1)}{= -4}$ ${x = -2}$